Particle acceleration by magnetic Rayleigh-Taylor instability: mechanism for flares in black-hole accretion flows

We study the magnetic Rayleigh-Taylor instability in relativistic collisionless plasma, as an astrophysical process for nonthermal particle acceleration. We consider dense plasma on top of a highly magnetized cavity with sheared magnetic field. Using particle-in-cell simulations, we show that small plumes grow and merge progressively to form a large-scale plume, which broadens to drive rapid magnetic reconnection in the cavity. We find that this leads to efficient particle acceleration capable of explaining flares from the inner accretion flow onto the black hole Sgr A*.